Biomechanical comparison of the 1.5mm locking compression plate with the 1.5 and 2.0mm mini-cuttable plates & Effect of bone-plate distance on the biomechanical properties of the 1.5mm locking plate

Biomechanical comparison of the 1.5mm locking compression plate with the 1.5 and 2.0mm mini-cuttable plates & Effect of bone-plate distance on the biomechanical properties of the 1.5mm locking plate

Author:

Watrous, Gwyneth

Department:

Department of Clinical Studies

Program:

Clinical Studies

Advisor:

Moens, Noel

Abstract:

This thesis documents a research study investigating the appropriateness of the 1.5mm locking compression plate (LCP) for repair of radial and ulnar fractures in miniature breed dogs. A retrospective study will review the current use and results of the mini-cuttable plates in miniature breeds while a biomechanical study compares the torsional and compression properties of the 1.5mm LCP to the 1.5mm mini-cuttable plate, 1.5mm mini-cuttable plate stacked and 2.0mm mini-cuttable plate. This thesis also documents effects of bone-plate distance on the biomechanical properties of the 1.5mm LCP in compression and torsion. A fracture gap model was created using a bone surrogate with a 1mm fracture gap and 6-hole plates. For the first phase, 16 constructs were made for each of the plates. Eight each were tested in compression and torsion. For the second phase, 32 constructs were made with the 1.5mm LCP but 16 constructs had a 0.5mm bone plate off-set and another 16 constructs had a 1mm bone plate off-set. The constructs were tested in compression and torsion. In compression testing, the 1.5mm LCP was similar in stiffness to the 2.0mm mini-cuttable, 1.5mm mini-cuttable and the 1.5mm mini-cuttable stacked plates. Conversely, the 1.5mm LCP was the weakest construct out of the four constructs tested for maximum load. Minimal displacement occurred during testing with the 1.5mm LCP compared to the other plates. In torsional testing, the 1.5mm LCP was equivalent to the stiffness of the 1.5mm mini-cuttable plate and the 1.5mm LCP was equivalent to the 1.5mm mini-cuttable and the 1.5mm mini-cuttable stacked for yield torque. All 1.5mm LCP constructs with 0.5mm or 1.0mm bone plate off-set resulted in significantly weaker constructs in compression and torsion and also showed evidence of early failure. This research study showed that the 1.5mm LCP was similar biomechanically to the 1.5mm mini-cuttable plate in compression and torsional testing. The use of the 1.5mm LCP can be considered as an option for radial fracture repair in dogs weighing less than 2.2kg where a 1.5mm mini-cuttable plate would otherwise be used. Bone plate off-set of either 0.5mm or 1.0mm for the 1.5mm LCP cannot be recommended.